12991997 has 4 divisors (see below), whose sum is σ = 13001856. Its totient is φ = 12982140.

The previous prime is 12991981. The next prime is 12992003. The reversal of 12991997 is 79919921.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 79919921 = 151 ⋅529271.

It is a cyclic number.

It is not a de Polignac number, because 12991997 - 2⁴ = 12991981 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12991967) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2579 + ... + 5712.

It is an arithmetic number, because the mean of its divisors is an integer number (3250464).

Almost surely, 2^12991997 is an apocalyptic number.

It is an amenable number.

12991997 is a deficient number, since it is larger than the sum of its proper divisors (9859).

12991997 is an equidigital number, since it uses as much as digits as its factorization.

12991997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9858.

The product of its digits is 91854, while the sum is 47.

The square root of 12991997 is about 3604.4412881888. The cubic root of 12991997 is about 235.0852082738.

The spelling of 12991997 in words is "twelve million, nine hundred ninety-one thousand, nine hundred ninety-seven".